The invention relates to the use of alkylated aminoethers to reduce the surface tension in water-based systems.
The ability to reduce the surface tension of water is of great importance in waterborne coatings, inks, adhesives, and agricultural formulations because decreased surface tension translates to enhanced substrate wetting in actual formulations. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Performance attributes resulting from the addition of surfactants include enhanced surface coverage, fewer defects, and more uniform distribution. Equilibrium surface tension performance is important when the system is at rest. However, the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are utilized. Such applications include spraying, rolling and brushing of coatings or spraying of agricultural formulations, or high speed gravure or ink-jet printing. Dynamic surface tension is a fundamental quantity which provides a measure of the ability of a surfactant to reduce surface tension and provide wetting under such high speed application conditions.
Traditional nonionic surfactants such as alkylphenol or alcohol ethoxylates, and ethylene oxide (EO)/propylene oxide (PO) copolymers have excellent equilibrium surface tension performance but are generally characterized as having poor dynamic surface tension reduction. In contrast, certain anionic surfactants such as sodium dialkyl sulfosuccinates can provide good dynamic results, but these are very foamy and impart water sensitivity to the finished coating.
There is a need for a family of surfactants which provide good equilibrium and dynamic surface tension properties, are low-foaming, are liquids at room temperature to facilitate handling and are stable under basic conditions and thus would be widely accepted in the coating, ink, adhesive, and agricultural formulation industries.
The importance of reducing equilibrium and dynamic surface tension in applications such as coatings, inks, and agricultural formulations is well-appreciated in the art.
Low dynamic surface tension is of great importance in the application of waterborne coatings. In an article, Schwartz, J. xe2x80x9cThe Importance of Low Dynamic Surface Tension in Waterborne Coatingsxe2x80x9d, Journal of Coatings Technology, September 1992, there is a discussion of surface tension properties in waterborne coatings and a discussion of dynamic surface tension in such coatings. Equilibrium and dynamic surface tension were evaluated for several surface active agents. It is pointed out that low dynamic surface tension is an important factor in achieving superior film formation in waterborne coatings. Dynamic coating application methods require surfactants with low dynamic surface tensions in order to prevent defects such as retraction, craters, and foam.
Efficient application of agricultural products is also highly dependent on the dynamic surface tension properties of the formulation. In an article, Wirth, W.; Storp, S.; Jacobsen, W. xe2x80x9cMechanisms Controlling Leaf Retention of Agricultural Spray Solutionsxe2x80x9d; Pestic. Sci. 1991, 33, 411-420, the relationship between the dynamic surface tension of agricultural formulations and the ability of these formulations to be retained on a leaf was studied. These workers observed a good correlation between retention values and dynamic surface tension, with more effective retention of formulations exhibiting low dynamic surface tension.
Low dynamic surface tension is also important in high-speed printing as discussed in the article xe2x80x9cUsing Surfactants to Formulate VOC Compliant Waterbased Inksxe2x80x9d, Medina, S. W.; Sutovich, M. N. Am. Ink Maker 1994, 72 (2), 32-38. In this article, it is stated that equilibrium surface tensions (EST""s) are pertinent only to ink systems at rest. EST values, however, are not good indicators of performance in the dynamic, high speed printing environment under which the ink is used. Dynamic surface tension is a more appropriate property. This dynamic measurement is an indicator of the ability of the surfactant to migrate to a newly created ink/substrate interface to provide wetting during high speed printing.
U.S. Pat. No. 5,098,478 discloses water-based ink compositions comprising water, a pigment, a nonionic surfactant and a solubilizing agent for the nonionic surfactant. Dynamic surface tension in ink compositions for publication gravure printing must be reduced to a level of about 25 to 40 dynes/cm to assure that printability problems will not be encountered.
U.S. Pat. No. 5,562,762 discloses an aqueous jet ink of water, dissolved dyes and a tertiary amine having two polyethoxylate substituents and that low dynamic surface tension is important in ink jet printing.
Gatto, et al., j. Org. Chem. 1986, 51, 5373-5383; Tetrahedron Letters 1986, 27, 327-330, describe several alkylated aminoethers of the form 
in which Rxe2x95x90Rxe2x80x2=CH2CH2OCH3, CH2Ph, CH2C6H4-2-OCH3, and CH2-2-furanyl. These compounds were used as intermediates for the synthesis of bibracchial lariat ethers.
Also described in the foregoing paper are compounds of the form 
where Rxe2x95x90Rxe2x80x2=(CH2)3CH3, (CH2)5CH3, CH2CH2OCH3, CH2Ph, and CH2-2-furanyl. These compounds were also used as intermediates for the synthesis of bibracchial lariat ethers.
Anelli and coworkers, J. Chem. Soc., Chem. Commun. 1983, 194-195; J. Org. Chem. 1984, 49, 4197-4203, describe alkylated aminoethers of the form 
where R=(CH2)3CH3. Also described by these workers are alkylated aminoethers of the form 
where R=(CH2)3CH3 or R=(CH2)7CH3. These materials were used for the preparation of double and triple bridged polyoxapolyazaheterophanes.
Bradshaw, Krakowiak and coworkers, J. Org. Chem. 1989, 54, 4061-4067; Tetrahedron Letters 1988, 29, 3521-3524; and J. Heterocyclic Chem. 1989, 26, 565-569, also describe aminoethers of the form 
where R=(CH2)3CH3 or CH2Ph. The benzyl derivatives were also described by Petranek and Ryba, Tetrahedron Letters 1977, 48, 4249-4250. The compounds were used as intermediates in the synthesis of polyaza crown compounds or other macrocycles.
Bradshaw and coworkers, Tetrahedron 1990, 46, 1163-1170, describe an alkylated aminoether of the form 
The N,Nxe2x80x2-dibenzyl derivative is also described here and by Duriez, et al., Tetrahedron 1992, 4347-4358. They are used as intermediates for the preparation of lariat ethers or other macrocyclic materials.
Hosgoren, et al., Collect. Czech. Chem. Commun. 1996, 61, 622-626, describe compounds of the type 
where R=CH3(CH2)6, CH3(CH2)7, CH3(CH2)8, or CH3(CH2)11. These compounds were used for the preparation of N,Nxe2x80x2-dialkyldiaza crown compounds.
U.S. Pat. No. 4,946,924 and U.S. Pat. No. 4,927,912 disclose compositions of the form 
wherein R is the nucleus of an oxyalkylation-susceptible polyhydric alcohol containing 2 to 12 carbon atoms and 2 or 3 hydroxyl groups, and Rxe2x80x2 is hydrogen or methyl, at least one of Rxe2x80x3 is isopropyl and the remainder of Rxe2x80x3 is hydrogen or isopropyl, n is a number sufficient to impart a molecular weight of about 200 to 400 to the molecule, and m is a positive integer having a value of 2 or 3. These amines are useful as curing agents for epoxy resins.
GB 2,191,419 discloses a structure of the form 
This material is reported to be useful in wash solutions for the selective removal of H2S and other S-containing compounds (e.g. COS, CS2, and mercaptans) from CO2-containing gases, especially natural gas and synthesis gas.
The alkylated aminoether of the form 
is reported in Acta Pol. Pharm. 1987, 44, 473-475, Acta Pol. Pharm. 1983, 40, 431 -434, and Acta Pol. Pharm. 1983, 40, 313-318 where it is used as a synthetic intermediate.
This invention provides water-based compositions containing an organic compound, particularly organic coating, ink, and agricultural compositions, having reduced equilibrium and dynamic surface tension by incorporation of an effective amount of an alkylated aminoether compound of the following structure:
Rxe2x80x94HN(CH2)p[O(CH2)n]mO(CH2)qNHxe2x80x94Rxe2x80x2
where n is 2-6, m is 0-4, and p and q are 2-6, and R and Rxe2x80x2 independently are an alkyl group comprising 5 to 18 carbons, preferably which is branched or in which the point of attachment to nitrogen is on a nonterminal carbon. Also provided is a method for lowering the equilibrium and dynamic surface tension of aqueous compositions by the incorporation of these alkylated aminoether compounds.
Also provided is a method for applying a water-based organic compound-containing composition to a surface to partially or fully coat the surface with the water-based composition, the composition containing an effective amount of an alkylated aminoether compound of the above structure for reducing the dynamic surface tension of the water-based composition.
There are significant advantages associated with the use of these alkylated aminoethers in water-based organic coatings, inks, and agricultural compositions and these advantages include:
an ability to formulate water-borne coatings, inks, and agricultural compositions which may be applied to a variety of substrates with excellent wetting of substrate surfaces including contaminated and low energy surfaces;
an ability to provide a reduction in coating or printing defects such as orange peel and flow/leveling deficiencies;
an ability to produce water-borne coatings and inks which have low volatile organic content, thus making these surfactants environmentally favorable;
an ability to formulate coating and ink compositions capable of high speed application;
an ability to formulate compositions which retain dynamic surface tension properties under strongly basic, high temperature environments.
an ability to formulate coatings, inks, and adhesives in which the surfactant is reactive during cure, reducing water sensitivity in the final products which arises from the presence of free surfactant.
Because of their excellent surfactant properties and low foam characteristics, these materials are likely to find use in many applications in which reduction in dynamic and equilibrium surface tension and low foam are important. Such applications include various wet-processing textile operations, such as dyeing of fibers, fiber souring, and kier boiling, where low-foaming properties would be particularly advantageous; they may also have applicability in soaps, water-based perfumes, shampoos, and various detergents where their marked ability to lower surface tension while simultaneously producing substantially no foam would be highly desirable.
This invention relates to the use of compounds of the formula
Rxe2x80x94HN(CH2)p[O(CH2)n]mO(CH2)qNHxe2x80x94Rxe2x80x2
where n is 2-6, preferably 2-4; m is 0-4, preferably 0-2; and p and q are 2-6, preferably 2 or 3; and R and Rxe2x80x2 independently are an alkyl group comprising 5 to 18 carbons, preferably 5 to 8 carbons which is branched or in which the point of attachment to nitrogen is on a nonterminal carbon, for the reduction of equilibrium and dynamic surface tension in water-based compositions containing an organic compound, particularly coating, ink, and agricultural compositions containing organic compounds such as polymeric resins, herbicides, pesticides or plant growth modifying agents. It is desirable that an aqueous solution of the alkylated aminoether demonstrates a dynamic surface tension of less than 45 dynes/cm at a concentration of xe2x89xa65 wt % in water at 23xc2x0 C. and 1 bubble/second according to the maximum-bubble-pressure method. The maximum-bubble-pressure method of measuring surface tension is described in Langmuir 1986, 2, 428-432, which is incorporated by reference.
The alkylated aminoethers can be prepared by reductive alkylation of the parent aminoethers with aldehydes and ketones using well-established procedures. The essential aspects of the preparation are the reaction of an aldehyde or ketone with the aminoether to make an imine or enamine intermediate which then reacts with hydrogen in the presence of a suitable hydrogenation catalyst to form the corresponding saturated derivative. 
The imine or enamine derivative may be preformed or may be prepared in situ.
The products could also be prepared by reductive amination of a suitable dinitrile. This reaction is illustrated for the cyanoethylated derivative of ethylene glycol: 
The reductive alkylation and reductive amination procedures are the methods of choice for the production of these materials, but the products may also be prepared by reaction of an amine with a chloralkylether. This reaction is illustrated for chloroethyl ether and an amine: 
Aminoether starting materials which are suitable for use in the reductive alkylation reaction include compounds of the form 
where n is 2-6, m is 0-4, and p and q are 2-6. Specific examples include aminoethyl ether; 1,2-bis-aminoethoxyethane; 2-aminoethoxyethyl ether; aminopropyl ether; 1,2-bis-aminopropoxyethane; 3-aminopropoxyethyl ether; and the like. The aminopropoxy compounds may be prepared by reaction of a diol with acrylonitrile, followed by hydrogenation: 
Suitable diols for use in the aminopropylation reaction include 1,2-ethanediol; 1,3-propanediol; 1,4-butanediol; 1,5-pentanediol, 1,6-hexanediol, and the like; diethylene glycol; triethyleneglycol; tetraethyleneglycol, and the like; dipropyleneglycol, tripropyleneglycol, and the like.
Alkyl groups which are suitable for use on the aminoethers should have sufficient carbon atoms to confer surface activity (i.e. an ability to reduce the surface tension of water) to the material but not enough carbon atoms to decrease the solubility to the extent that the ability of the material to reduce surface tension is insufficient for a particular application. In general, an increase in the carbon number increases the efficiency of the resulting alkylated aminoether surfactant (i.e., less surfactant is required to obtain a given decrease in surface tension) but decreases its ability to reduce surface tension at high surface creation rates (i.e., less effective for reducing dynamic surface tension). The latter effect is a result of the fact that increased carbon number generally decreases the water solubility of the material, and consequently, diminishes the diffusive flux of surfactant to newly-created surface. Generally, in the practice of this invention, it is desirable to use alkylated aminoethers having a solubility in water of at least 0.005 wt %, preferably from 0.01 to 2 wt %, and most preferably from 0.05 to 1.5 wt %.
The alkyl groups may be the same or different. They may be branched or the point of attachment to the nitrogen of the diamine may be on an internal carbon. Suitable alkyl groups are derived from reductive alkylation reactions of a C5 to C8 aldehyde or ketone, preferably derived from reductive alkylation reactions of methyl isobutyl ketone or methyl isoamyl ketone. Specific examples of suitable C5 to C8 aldehydes and ketones include 2-pentanone, 3-pentanone, pivaldehyde, methyl isopropyl ketone, 2-hexanone, 3-hexanone, methyl tert-butyl ketone, ethyl isopropyl ketone, 2-methylhexanal, 2-heptanone, 3-heptanone, 4-heptanone, 2-octanone, 3-octanone, 4-octanone, 2-ethylhexanal, and so on. The specific carbonyl compound and aminoether chosen will depend on the surfactant properties required for a particular application.
The alkylated aminoethers are suitable for use in an aqueous composition comprising in water an inorganic compound which is a mineral ore or a pigment or an organic compound which is a pigment, a polymerizable monomer, such as addition, condensation and vinyl monomers, an oligomeric resin, a polymeric resin, a detergent, a herbicide, a pesticide, or a plant growth modifying agent. An amount of the alkylated aminoether compound that is effective to reduce the equilibrium and/or dynamic surface tension of the water-based inorganic and/or organic compound-containing composition is added. Such effective amount may range from 0.001 to 20 g/100 ml, preferably 0.01 to 2 g/100 ml, of the aqueous composition. Naturally, the most effective amount will depend on the particular application and the solubility of the alkylated aminoether.
In the following water-based organic coating, ink, and agricultural compositions containing an alkylated aminoether according to the invention, the other listed components of such compositions are those materials well known to the workers in the relevant art.
A typical water-based organic coating composition to which the alkylated aminoether surfactants of the invention may be added would comprise the following components in an aqueous medium at 30 to 80% solids:
A typical water-based ink composition to which the alkylated aminoether surfactants of the invention may be added would comprise the following components in an aqueous medium at 20 to 60% solids:
A typical water-based agricultural composition to which the alkylated aminoether surfactants of the invention may be added would comprise the following components in an aqueous medium at 0.1 to 80% ingredients: